The invention is in the field of multiple photoflash lamp units, such as planar arrays.
U.S. Pat. No. 3,894,226 to James M. Hanson describes a planar photoflash array in which flash lamps are connected to a circuit board containing thereon radiation-sensitive switching circuitry for sequentially flashing the lamps. An electrically conductive reflector unit is positioned between the lamps and the circuit board. The lamps, circuit board, and reflector unit are enclosed in a plastic housing, and the array is provided with connector means for connecting it to a camera or other device for applying firing voltage pulses to the array.
A flash array of the type just described, which is available in stores and is called "Flip Flash," utilizes so-called high voltage lamps which are flashed by high voltage pulses of a few thousand volts, at a low energy, such as can be produced by stressing a piezoelectric element contained in a camera or flash adapter. Since persons and objects can become electrostatically charged to several thousand volts (at low energy), especially in dry weather, there could be a problem of lamps accidentally flashing due to electrostatic charge when the array is handled or touched, by a charged person or object, in the vicinity of a lamp or certain parts of the sequencing circuit. This is due to the electrostatic discharge being coupled to or passing through the primers in one or more of the lamps, the primers constituting chemical material for igniting the lamps in response to a suitable voltage.
Some of the above-mentioned patent applications disclose techniques for reducing the likelihood of accidental electrostatic flashing of the lamps, including an electrically conductive reflector unit connected to electrical ground of the circuit, and additional electrical shielding means, and circuitry arrangements and connections. The last referenced Cote patent application discloses an arrangement of openings through the array housing wall, at locations near electrical ground in the array, to provide preferential paths for electrostatic discharges to the electrical ground instead of to sensitive places in the lamps or circuitry.